What is Extrinsic Allergic Alveolitis (Hypersensitivity Pneumonitis) ?

Hypersensitivity Pneumonitis
Extrinsic allergic alveolitis (synonym: hypersensitivity pneumonitis) describes an interstitial and bronchioloalveolar disease of the lungs caused by an immune mediated hypersensitivity response. It is associated with repeated exposure to a variety of inhaled organic dusts and reactive chemicals (allergy chemical), but only a proportion of exposed subjects become affected. Notable examples are farmers’ lung (due to actinomycetes contaminating farm produce) and bird fanciers’ lung (due to secreted avian antigens). The disease has considerable potential as a model of allergic lung disease, since the populations at risk can often be identified precisely, the relevant antigens can be purified, and the clinical and immunologic consequences of antigen exposure can be examined. (more…)